Low p-type surface concentrations were introduced at high temperatures by using a Ga-Cd alloy as a diffusion source. Concentration profiles were determined by using electrochemical profiling techniques. The resultant profiles were of erfc-type. It was found that the surface concentration of the carriers was reduced if diffusion was carried out by using Ga-Cd alloys which contained less than 1at%Cd. Results which could be described by:

D(cm2/s) = 1.10 x 10-13 exp[-2.12(eV)/kT]

were found when pure Cd was used as a diffusion source, together with a 5nm SiO2 over-layer. When Ga-1at%Cd alloy was used as a source, at temperatures of 800 and 850C, the diffusivities were 8.2 x 10-15 and 2.54 x 10-14cm2/s, respectively; thus suggesting that the diffusivity could be described by:

D(cm2/s) = 1.29 x 10-14 exp[-2.17(eV)/kT]

The surface concentration could be further reduced to 1017/cm3 if an 0.1at%Cd alloy was used. In this case, the diffusion coefficient at 850C was 1.45 x 10-14cm2/s.

D.K.Gautam, Y.Nakano, K.Tada: Japanese Journal of Applied Physics, 1991, 30[6], 1176-80